Centrifugal contactor



Jan. 7, 1958 R. T. VAUGHAN 2,819,015

CENTRIFUGAL CONTACTOR Fild Nov. 19, 1951 2 Sheets-Sheet 1 6 Mai.

Jan. 7, 1958 R. 'r. VAUGHAN CENTRIFUGAL CONTACTOR 2 Sheets-Sheet 2 Filed NOV. 19, 1951 United States CENTRIFUGAL CONTACTOR Robert T. Vaughan, Rockledge, Pa., assignor to The Sharples Corporation, a corporation of Delaware Application November 19, 1951, Serial No..25.7,129

6 Claims. (Cl. 233-) This invention relates generally to apparatus for the countercurrent contact of liquids, and particularly to the utilization of centrifugal force for contact and separation purposes.

This application relates to the type of centrifugal contactor described and claimed in Zabriskie application Serial No. 257,102, filed November 19, 1951.

Many types of equipment are now used for liquid/ liquid extraction. One type comprises a series of mechanical mixers followed by gravity or centrifugal separation, each operation of'mixing and settling constituting one stage, with multiple stages created by a multiplicity of mixing and separating steps, fresh solvent being introduced into the series in the stage most remote from the introduction of the feed of liquid to be extracted. Mixing may be done with some form of mechanical agitator or with pump recirculation. This system is faulty in that such mixing gives relatively poor contact eficiency. Attempts to improve contact by intensifying and prolonging the agitation frequently produce emulsions that are difficult or impossible to break.

Perhaps the most widely used device consists-of a tower packed with selected material such as glass balls, 'Raschig rings, short cylinders, or other special ceramic shapes. The lighter liquid is introduced at the bottom of the tower and passes upward while the heavier liquid is fed at the top and passes countercurrently downward. Packing is ordinarily selected of akind that one'of the liquids will wet and thus comprise the dispersed phase, whereas the other will comprise the continuous phase.

Other forms of extractors are well known in the art, but many of these require a great deal of floor space and/or headroom, and most of them are so constructed that cleaning deposits is a major and time-consuming operation.

Aprincipal object of this invention is to provide an improved countercurrent extraction method and apparatus that have highly efiicient separation between mixing stages, and .a high potential throughout per unit area.

A further object of this invention is to provide means of separating the mixing and settling stagesin a contractor of the type described, said means serving to reduce the relative axial length of the settling stage as compared to the mixing stage.

A further object of this inventon is to provide an improved double bafile located between mixing and settling stages of the centrifugal contactor whereby turbulence is reduced and recirculation is increased.

Another object of the invention is to provide means for the mixture to flow from each mixing zone into each separating zone without opportunity for Stratification in the mixing zones.

Another object of this invention is to provide means to prevent direct transmission ofturbulence from the mixing zones into the separating zones.

.Another objectotthe "invention is to provide means for extremely intimate contacting of one liquid with the other, without forming emulsions that are diflicult to separate.

Another object of the invention is to provide an appa ratus that has constant separating force and agitation intensity throughout the full countercurrent cycle.

Fields in which this method and apparatus are most useful include antibiotic production, including extraction from broth; extraction and purification of vitamins, hormones, amino-acids, and other pharmaceuticals; separation of close boiling-point hydrocarbons, as in the extraction of toluene or butadiene from hydrocarbon mixtures such as hydro-former eflluent; extraction of oxygenated compounds from synthetic gasoline, and isomer separation of such compounds as the nitrotoluencs; recovery of organic acids such as citric, lactic, and acetic acid from aqueous solutions; purification of such organic materials as rosin, glycerine; washing of gasoline distillates to remove sulfur and mercaptans; vegetable oil tractionating; water cleanup of dilute solutions of aniline, phenol, cresol.

In order that the invention may be readily understood, reference is made to the accompanying drawings, forming part of this specification.

Fig. l is a vertical section of a countercurrent contactor illustrating one form of the invention;

Fig. 2 is an enlarged sectional detail as seen at 2-2 of Fig. 1;

Fig. 3 is a sectional detail as seen at 33 of Fig. 2; and

Fig. 4 is a sectional detail as seen at 4-4 of Fig. 3.

The invention comprises essentially the provisionof a plurality of relatively narrow chambers in axial spaced relation in the rotor between the separating zones, together with suitable baffles between the chambers for introducing recirculation and minimizing turbulence. The liquids are introduced countercurrently into these chambers where they are agitated by means of a stationary vane or blade. This agitation intimately contacts a solvent with a liquid to be extracted. The intimate contact is followed by a separating step and the process may be repeated in a plurality of zones, each mixing and separating step constituting one stage.

Referring to Fig. 1, the assembly comprises a Vertically mounted rotor 9 shown as having a removable rotor top 10 and a removable rotor bottom 11. In the rotor bottom 11 andattached thereto are a plurality of vanes 12 which assist infeeding liquid through passages 86 into the bottom of rotor 9.

The rotor top 10 has a plurality of discharge channels 21 which form passages between the interior of the rotor ii and an annular collecting chamber 22. The channels 21 are inclined with respect to the rotor so that the upper ends of the channels are near the axis of the rotor. A piloted driveshaft 24 is secured to the upper end of the rotor top 10 by means of a shoulder nut 25. The shaft 24 and rotor 9 aredriven by any suitable form of motor or other device (not shown).

Rotor top 10 is provided with a chamber 23 having a bottom 31 containing a ferrule 32 in which is positioned a sleeve bearing 33. Bearing 33 may be of the self-lubrieating type or lubricated by the inflowing liquid, or it may be replace'd by a ball bearing with proper mounting, or auy other suitable type'of bearing.

The rotor bottom ll extends at 11a into the bore of a self-lubricating bearing 35. A spring 36 keeps the hearing 35 firmlyfixed against the upper inside of the shell 37 through pressure exerted against collar 38 to which the shell 37 is threaded. Collar 38 is removably mounted in lower supporting member 41.

A stationary conduit43 extends through the center of collar 38 at thebottom of the countercurrent contactor, and through bearing 33 atthe top. The bottom section of conduit 43 is divided into two passages by means of an axially extending wall or baflie 44 so that heavy liquid introduced into passage 43a through coupling 45 flows upwardly through the passage and out of orifice 46. The light liquid is introduced into the conduit 43 through coupling and flows upwardly through the bore of conduit 43 to chamber 28 (Fig. 1). In this manner, the heavy liquid flows upwardly through rotor 9 and is discharged through passages 21 into collecting chamber 22 and thence into spout 48. The chamber 22 is of conventional design and is supported in a stationary member 49. The depth of the heavy liquid in rotor 9 is controlled by the diameter of an annular ring darn 50 secured to rotor top by means of a nut 51 and is provided with a gasket 52.

The rotor 9 (as shown in Fig. 1) includes a plurality of mixing assemblies 53, 53 which are axially spaced in the rotor between separating zones 55, 55 and 56, 57. The conduit 43 forms the central supporting structure in the rotor and the mixing assemblies 53, 53 are axially spaced by vane assemblies 58, 59, 60, and 61. Assemblies S9 and 60 at the center of the rotor are identical, each one comprising a sleeve 62 substantially larger in diameter than conduit 43, to which three radially extending vanes 63, 63 are secured as by welding. The vanes 63 have frictional engagement with the inner wall of rotor 9 (Fig. 2). The lower vane assembly 58 is slightly modified in that the sleeve 64 terminates substantially short of the lower ends of the vanes 65, 65 and in this case the vanes extend inwardly close to the conduit 43. The vanes 66 of upper assembly 61 likewise extend somewhat beyond the sleeve 67 and abut the bottom of the rotor top 10. It will be understood that the various mixing assemblies 53, 53 and the vane assemblies 58-61 are axially compressed between and held in place by the rotor bottom 11 and the rotor top 10.

Each of the mixing assemblies (Figs. 2, 3, and 4), all of which are identical, comprises an upper pair of spaced baffles 70 and 71 which are riveted and held in spaced relation by rivets 72 and spacers 73. Uppermost baffle 70 has a plurality of radially positioned apertures which may be in the form of slots 74, 74 which are similar to, but out of axial alignment with, radial slots 75, 75 in bafiie 71 (Fig. 2). The lower baffles 76 and 77 are exactly the same as baffles 70 and 71, baflle 76 having slots 78, 78 and baffle 77 having unregistered slots 79, 79. Baffles 76 and 77 are similarly secured to each other in spaced relation by means of rivets 80 and spacers 73a, 73a.

Battles 70, 71, 76 and 77 are positioned in equal axial spaced relation from each other by spacing collars 81, 81 and also from the stirring blades 82. Each stirring blade 82 is diamond-shaped (as shown in Fig. 4) and is held stationary on conduit 43 by means of spacing sleeves 83, 8.3, the bottom sleeve 83 being welded to the outside of conduit 43 as shoWn in Fig. l, and the top sleeve being retained on the conduit by means of a threaded collar 84.

Fig. 1 shows a centrifugal contactor having three mixing assemblies interposed between four separating zones as previously described. It will be understood that the present invention is not limited to any specified number of separating zones and mixing chambers since the proper selection depends upon the conditions present and the materials being processed.

.As previously stated, the inside diameter of ring. 50 in rotor top 1%) controls the depth of the heavy liquid in the separating zones. The total depth of liquid however is controlled by the inside diameter of annular ring a in bottom closure 15 and the location of the dividing line between the heavy and light phases depends upon the ratio of the total weight of the light and heavy phases beneath annular flanges 10a of rotor top 10 and the weightof the heavy phase above flange 10a, as determined bythe inside di etcr of ring 50. Increasing the diameter of ring 50 displaces the dividing line between the light and heavy phases outwardly in the rotor, thus reducing the depth of the heavy layer. Decreasing the inside diameter of ring 50 conversely increases the depth of the heavy layer. Similarly, the use of diiferent closures 150! having various inside diameters controls the total depth of the liquid in the rotor; the smaller the diameter the greater the total liquid depth.

In operation, the rotor is brought up to the normal operating speed, for example 17,000 R. P. M. Since this speed is above the critical for the rotating parts, moderate clearance is provided between bearing 35 and shell 37 to permit the shifting of the rotor on its axis so that the center of rotation corresponds with the center of the mass. Chattering is inhibited by compression spring 36.

The heavy liquid is introduced through coupling 45 and through conduit 43a, at a pressure sufficiently high to overcome back. pressure due to friction loss in conduit 43a. The heavy liquid then discharges from orifice 46 where it is directed by vanes 12 through one or more axial passages 86 into the first separating zone 56. The heavy liquid then continues to travel upwardly through the various stages comprising the mixing assemblies 53, 53 and zones 55, 56, and 57. It is finally delivered through channels 21 into collecting chamber 22.

The lighter liquid is likewise introduced under pressure to the bore of conduit 43 through coupling 47. This liquid however is forced to the top of conduit 43 into chamber 28 whereupon it flows downwardly into separating zone 57 through passages 87 in chamber bottom 31. The lighter liquid passes progressively downward through the various separating zones and mixing assemblies and is finally delivered past ring 1511 into chamber 14 and out of passage 88 into the lower collecting chamber 89, supported on stationary member 90. The light liquid is thereupon discharged from spout 91. It will thus be understood that the light and heavy liquids travel in countercurrent directions and each liquid is successively subjected to separation under high centrifugal force and intense a itation at high speed.

Referring now particularly to Figs. 2-4, the operation of the mixing assemblies which create separate stages or mixing zones for the liquids will be more fully described. It will be noted that the slots 74 and 75 in baffles and 71 as well as the slots 78 and 79 in lower bafiles 76 and 77 preferably extend radially substantially throughout the thickness of the liquid Wall. In this way, both the heavy and light liquids are introduced into the mixing chamber 92 where contact with stirrer blade 82 reduces the rotational velocity at the surface of the blade and this in turn results in less pressure due to centrifugal force at the surface of the blades than at a point outside the mixing zone or chamber 92. This differential in pressure results in circulating the liquids in a path shown generally by the arrow in Fig. 3. It will be understood that similar paths are followed adjacent to each of the apertures in the zone. Liquid that is thus broken into a discontinuous state due to the agitation of the stationary stirrer blade, moves outwardly away from the blade at a point nearer the center of the rotor and is replaced by a flow of liquid that is in a continuous state under the influence of centrifugal force. This circuit by alternately converting the liquid from a discontinuous to a continuous state provides more intimate contact than would be the case if the continuous phase passed directly through the mixing zone without such recirculating. Nevertheless, there is a steady flow of the liquids countercurrently through the length of the rotor because each one is displaced by more incoming liquid at the respective feed ports.

An important feature of the present construction resides in the relative location of the slots 78 and 79, and 74 and in the baflles. By locating these slots in the respective baflie pairs out of registry, the turbulence in the mixing zone is not carried over into the adjacent separating zones because the agitated liquids must pass through 0 the outer baflies 70 and 77 as the case may be. There is asigois i ample opportunity for turbulence to be decreased or minimized before the liquids enter into their respective contiguous separating zones. This "permits centrifugal separation in these zones to be highly effective.

The present construction was particularly designed to permit quick disassembly of the rotor so that all parts may be satisfactorily cleaned. Such cleaning becomes highly important when the liquids leave deposits or when the liquids decompose. Many applications require quite frequent cleaning in order to avoid contamination of the product.

It will thus be understood that I have described an apparatus and a process which utilize novel structure in quickly and efliciently subjecting two liquids which flow in opposite directions through a rotor, to high separation under centrifugal force, followed by intense agitation of both liquids to break up the separation periodically. While the exact reason for the better results achieved is not completely understood, it is believed that the transfer coefiicient is at a substantial maximum immediately after agitation and that continued agitation after a specified time interval does not materially increase such transfer. However, coalescence followed by further agitation permits further transfer, and the recirculating at each stirrer blade as described above, thus affords an opportunity for extremely effective extraction in each stage.

While embodiments of the process and apparatus have been more particularly described, it is to be understood that this is by way of illustration, and that changes, omissions, additions, substitutions and/or modifications may be made by persons skilled in the art upon becoming familiar herewith, and without departing from the spirit of the invention. For instance, for purposes of illustration, the heavier phase is described as flowing upwardly through the rotor, while the lighter phase flows downwardly, and apparatus to eifect this purpose has been particularly described. However, it will be well understood by persons skilled in the art that the apparatus may be modified in a manner to cause the heavier phase to flow downwardly while the lighter phase flows upwardly through the rotor. Then too, the rotor may revolve about any other axis such as horizontal or even inclined as also will be well understood. Also for purposes of illustration, with accompanying simplicity of construction, the conduit 43 has been described as being held stationary along with the stirring blades 82 mounted thereon. Since, broadly speaking, all that is required is relative rotational movement between the rotor and the blades 82, it follows that such relative rotational movement may be brought about in any desired way. Thus blades 82 may be caused to rotate either in the same direction as the rotor but at a different rate, or in a direction opposite to the direction of rotation of the rotor. These variables in relative totational movement between the mixing devices or blades and the rotor make available any desired degree of mixing or agitation, irrespective of the speed of rotation of the rotor, with increased versatility in the application of the invention. Many other modifications or embodiments will suggest themselves to persons skilled in the art upon becoming familiar herewith.

I claim:

1. In a centrifugal machine of the type having a rotor, a plurality of stages in said rotor, said stages comprising successive mixing and separating zones, the sub-combination which comprises a mixing zone assembly having a central shaft running therethrough, a blade mounted on said shaft, a first baflie assembly driven by the rotor and mounted in axial spaced relation to the blade, at second baffle assembly driven by the rotor and mounted in axial spaced relation on the opposite side of said blade, each of said baffie assemblies comprising spaced bafile plates having a plurality of apertures therein for permitting complete flow of liquid in either direction through the mixing zone assembly with the apertures in one baffle plate of the bafile assembly positioned out of axial align- :6 ment with the apertures in another b'aflie plate of said bafile assembly, andmeans for 'efiecting relative-rotational movement between said shaft and saidrotor.

2. In a countercurrent centrifugal contactor having a rotor, means for driving said rotor, and means for flowing partially miscible liquid phases of diiferent density countercurrently through said rotor, the improvement which comprises means for flowing each of said phases predominantly unidirectionally through said rotor in contact with the other of said phases including means in said rotor at each end thereof for centrifugally separating said phases, mixing means Within said rotor intermediate said last-mentioned means for mixing said phases, and baflle means on each side of and adjacent said mixing means for recirculating a portion of each of said phases back into said mixing means.

3. The combination with a countercurrent centrifugal contactor having a rotor, means for driving said rotor, and means for flowing partially miscible liquid phases of different density countercurrently through said rotor, of means for flowing each of said phases predominantly unidirectionally through said rotor in contact with the other of said phases including means in said rotor at each end thereof for centrifugally separating said phases, mixing means Within said rotor intermediate said lastmentioned means for mixing said phases, and perforated spaced bafiles positioned on each individual. side of and adjacent to said mixing means, said oafiles being rotatable with said rotor and extending transversely of said rotor across the paths of flow of said phases with the perforations of each bafile falling within said paths of flow and with the perforations in adjacent battles on each individual side of said mixing means axially out of register with respect to each other.

4. A countercurrent centrifugal contactor comprising a rotor, means for feeding a liquid phase to one end of said rotor, means for feeding another liquid phase to the other end of said rotor, means for maintaining countercurrent flow of said phases with respect to each other through said rotor and for discharging said phases in separated condition from said rotor, a plurality of axially spaced phase mixing means within said rotor for intimately mixing said phases while undergoing said countercurrent flow, perforated spaced bafiies positioned on each individual side of and adjacent to each said mixing zone, said bafiles being rotatable with said rotor and extending transversely of said rotor across the paths of flow of said phases with the perforations of each baffle falling within said paths of flow and with the perforations in adjacent bafilcs on each individual side of each said mixing zone axially out of register with respect to each other, and a plurality of axially spaced phase separating means in said rotor adapted to maintain predominantly unidirectional flow of said phases, each phase mixing means having a phase separating means on each side thereof with said perforated spaced bafi'les inbetween.

5. In a centrifugal machine of the type having a rotor, and inlet and outlet liquid passages for said rotor, the sub-combination which comprises a shaft extending axially through said rotor and concentric therewith, a plurality of stirring blades mounted on said shaft, means for retaining said blades in axial spaced relationship to each other, bafile assemblies mounted in said rotor and rotatable therewith with a baffie assembly positioned in axial spaced relationship on each side of and adjacent to each blade, means for axially spacing the baffles of each baffle assembly with respect to each other, a plurality of radially elongated apertures in each battle of said baflle assembly with the apertures in one battle of the baffie assembly completely out of axial alignment with the apertures in an adjacent baffle of said b aille as sembly, phase separating means on each side of each of the baffle assemblies and rotatable with the rotor, and References Cited in the file of this patent means for efiecting reletive rotational movement be- UNITED STATES PATENTS tween said shaft and sald rotor. t

6. The sub-combination of claim 5 wherein the phase 2,036,924 coutor 1936' separating means are vane assemblies. 5 21234921 Webb 1941 

